The Supreme Court will hear Hobby Lobby's religious liberty challenge to Obamacare on Tuesday. Its decision could have far-reaching consequences.

WASHINGTON — A challenge to part of President Obama's healthcare law that hits the Supreme Court on Tuesday could lead to one of the most significant religious freedom rulings in the high court's history.

Four years ago, in their controversial Citizens United decision, the justices ruled that corporations had full free-speech rights in election campaigns. Now, they're being asked to decide whether for-profit companies are entitled to religious liberties.

At issue in Tuesday's oral argument before the court is a regulation under the Affordable Care Act that requires employers to provide workers a health plan that covers the full range of contraceptives, including morning-after pills and intrauterine devices, or IUDs.

The evangelical Christian family that controls Hobby Lobby Stores Inc., a chain of more than 500 arts and crafts outlets with 13,000 workers, says the requirement violates its religious beliefs.

Some contraceptives can "end human life after conception," the Green family says. Forcing the owners to pay for such devices would make them "complicit in abortion," their lawyers say.

A ruling in their favor could have an effect on tens of thousands of women whose employers share the Greens' objections to some or all contraceptives.

But the case could also sweep far beyond just this one provision of Obamacare. The justices have been wary of accepting claims that religious beliefs can exempt people — or companies — from following laws that apply to everyone. The court's previous religious freedom cases usually involved narrowly focused claims from religious minorities, such as the Amish or Seventh-day Adventists.

But the current court, led by Chief Justice John G. Roberts Jr., has shown a greater interest in religious freedom claims. And because the objections to the contraceptive mandate come from Catholic bishops and evangelical Christians, not small or obscure sects, the potential effect has been magnified.

The Obama administration argues that if the justices allow Hobby Lobby to refuse to pay for contraceptives because of its owners' religious beliefs, the way would open for religious objections to a broad array of laws. Companies potentially could shape the benefits they offer, and perhaps even their hiring, based on their religious convictions.

Gay rights advocates worry such a ruling could give businesses a right to deny services to customers or clients.

The White House already has made concessions on the contraceptive rule to accommodate religious beliefs. It exempted churches and religious bodies entirely and said nonprofit groups with religious affiliations, such as Catholic hospitals or colleges, need not pay for contraceptives directly. The duty falls to their insurance providers.

But Obama and his advisors drew a line at for-profit corporations like Hobby Lobby.

There is not "a single case in this nation's history in which a commercial enterprise" has won a right based on religious beliefs to be exempt from regulations that govern for-profit corporations, government lawyers have said in a brief for the court.

The legal battle has played out across the country. In addition to Hobby Lobby, about 50 other for-profit companies large and small have sued to gain a religious exemption from the contraceptive rule.

The suits rely not just on the 1st Amendment, but also on a law Congress passed in 1993 to strengthen religious freedom. That law, the Religious Freedom Restoration Act, says the "government shall not substantially burden a person's exercise of religion," except to further a "compelling" interest.

Not surprising, the two sides differ on what that means. Lawyers for Hobby Lobby say the Greens exercise their religion in the way they control their company. That puts the company under the law's protection, they argue.

"The Greens allow their faith to guide business decisions. All Hobby Lobby stores close on Sundays, at a cost of millions per year, to allow employees a day of rest," they told the court. The Greens also operate a separate chain of Christian book stores.

Women's rights advocates who support the administration argue that corporations are legally separate from the people who own them.

"The key question is whether a corporation can have a religion," said Judy Waxman, a vice president of the National Women's Law Center.

Supporters of the healthcare law also argue that the government has compelling reasons to require contraceptive coverage. Long-term contraceptives like IUDs are far more effective than other, less costly methods of birth control, but many women cannot afford them if they are not covered by insurance, healthcare experts say.

"Half of the pregnancies in this country are unplanned," said Dr. Hal C. Lawrence III, chief executive of the American Congress of Obstetricians and Gynecologists. Wider availability of effective contraceptives "prevents unintended pregnancies and, of course, abortions."